During the last year our research core has worked with nine NIH research units to generate novel embryonic stem cell lines (28 projects) and new mouse models (19 projects). This research included establishment of models to study neurogenesis in developing and mature brains, RNAse H biology and pathology, signal pathway interactions in the immune system, T cell development, hematopoiesis, stem cell biology, epigenetic inheritance in the early embryo, RNA metabolism, genetic disorders in bone and extracellular matrix, gene regulation and enhancer function, and endocrine and cancer genetics. We also performed cryopreservation of 8 mouse lines for two research units.